1. Field of the Invention
The present invention relates to high density synthetic sponges, such as polyvinyl alcohol sponges. More specifically, the invention is high density synthetic sponge and a method and apparatus for rinsing a high density synthetic sponge which reduces processing residue and particulate matter to render the sponge biocompatible.
2. Description of the Related Art
The use of synthetic sponges, such as polyvinyl alcohol (or polyvinyl acetal) sponges, is well-known. For example, synthetic sponges have been used as cleaning rollers for cleaning semiconductors or the like. Also, synthetic sponges have many medical applications. For example, synthetic sponges are used as bandages, sanitary napkins, diagnostic swabs and general surgical sponges. Also, specialty surgical sponges have been developed for use in orthopedic, vascular, plastic, eye, ear, nose, throat, and other surgical procedures. Polyvinyl alcohol sponges are used in many surgical applications. For example, surgical "spears" or "points" are small triangular sponges used during ophthalmic or other surgical procedures to absorb small amounts of liquid. Sometimes, the triangular sponges are mounted on a handle to facilitate manipulation. Ordinarily, surgical spears are made of cellulose sponge material or polyvinyl alcohol sponge material.
Conventionally, pores are formed in synthetic sponges by pore forming chemical additives such as starch and sulfate mixtures, or by injecting gas into solution during the chemical reaction used to form the sponge. In surgical applications, the sponge must be biocompatible, i.e. free of processing residue and particulate matter. Therefore, the sponge is subjected to a series of rinsing steps to remove reactant chemical residue and a particulate matter. One type of sponge currently used in surgical applications, is a polyvinyl alcohol sponge sold as the MEROCEL sponge manufactured by MEROCEL Scientific Products. The density of the MEROCEL sponge, when dry, is generally in the range of 0.70 g/in.sup.3 to 1.60 grams/in.sup.3. This range of densities has proven useful for many applications including sinus packing, otic products, and ophthalmic products, such as spears. However, in certain applications, it is desirable to use a synthetic sponge having a relatively high rigidity, and thus a higher density, to facilitate moving or holding tissue with the sponge.
Another available sponge is a fine grade cellulose sponge sold under the trade name WECKCEL. Cellulose sponges are absorbent and relatively rigid but have a high amount of particulate matter and thus can leave debris at the operative sight. Of course, it is desirable to form synthetic sponge material having a relatively high rigidity and a low amount of a particulate matter. However, a high rigidity necessarily requires a high density and thus presents processing problems. Specifically, when forming sponges of a relatvely high density, the pores in the sponge must be relatively small. When a sponge with small pores is formed, it is a very difficult to rinse processing chemical residue and particulate matter from the pore space because rinsing solution does not readily enter and leave the small pore spaces. Therefore, it is desirable to obtain a synthetic sponge, such as a polyvinyl alcohol sponge, having a relatively high density, above 2 grams per cubic inch in a dry state for example, and also having very low chemical residue and particulate matter. Also, it is desirable to obtain a synthetic sponge having an improved surface, i.e. smoother, texture to avoid damage to sensitive tissue, such as ophthalmic tissue, during use.